1. Field of the Invention
The present invention relates a forming mold for a lens sheet such as a Fresnel lens sheet and a method for manufacturing such a forming mold.
2. Description of the Related Art
Japanese Laid-Open Patent Application Nos. S64-86102, H6-67002 and H7-148751 disclose a method for manufacturing various kinds of lens sheet such as Fresnel lens sheets, lenticular lens sheets or the like, which are to be used for a transmission type screen for a projection TV.
Description will be given below of the above-mentioned conventional method for manufacturing a lens sheet with reference to FIG. 7. First, ultraviolet ray curing type resin in the form of liquid is applied on a forming mold 2 on a pressing-finishing side thereof to form an uncured resin pool 3 (see FIG. 7(A)). A sheet-shaped substrate 4 is placed on the forming mold from above the uncured resin pool 3 of the ultraviolet ray curing type resin (see FIG. 7(B)). Then, the substrate 4 and the forming mold 2 are pressed together by means of a pair of pressing rollers 5a, 5b so as to flatten the uncured resin pool 3 to form a laminate structure of the substrate 4 and the ultraviolet ray curing type resin 3, while excluding bubbles from the ultraviolet ray curing type resin 3 (see FIGS. 7(C) and 7(D)). Then, ultraviolet ray 7 is irradiated on the ultraviolet ray curing type resin 3 through the substrate 4 to cure it (see FIG. 7(E)). Then, the cured resin 3 is peeled together with the substrate 4 from the forming mold 2, thus manufacturing a lens sheet 1.
In such a conventional method, pressing the substrate 4 and the forming mold 2 during the lamination step as shown in FIGS. 7(C) and 7(D) causes a superfluous amount of resin 3a of the ultraviolet ray curing type resin 3 to flow from the periphery of the forming mold 2, thus sagging downward from the forming mold 2 as shown in FIG. 7(D). Such a superfluous amount of resin 3a may be left on the periphery of the forming mold 2 even when the lens sheet 1 as the finished product is peeled from the forming mold 2. The above-mentioned superfluous amount of resin 3a may adhere on a molding surface of the forming mold 2 when manufacturing the new lens sheet with the use of the above-mentioned forming mold 2 or be entrapped into the ultraviolet ray curing type resin 3 as newly applied on the molding surface, thus deteriorating formability of the lens sheet 1. The superfluous amount of resin 3a may drop in an uncured state from the forming mold 2 on a traveling passage for the forming mold 2 and the other equipment, making them dirty and disturbing transfer of the forming mold 2.
An object of the present invention is therefore to provide a forming mold for a lens sheet, by which the above-mentioned problems can be solved, and a method for manufacturing such a forming mold.
In order to attain the aforementioned object, a forming mold of the present invention for a lens sheet, which is to be used for molding ionizing radiation curing type resin into the lens sheet by applying said resin in a form of liquid on an upper surface of said forming mold, placing a substrate on said resin and pressing said substrate and said resin against said forming mold from a pressing-starting side of said forming mold to a pressing-finishing side thereof by means of a pressing roller, comprises:
a mold body; and
a receiving member for receiving a superfluous amount of the ionizing radiation curing type resin, said receiving member being provided on at least said pressing-finishing side of a periphery of said mold body.
According to the above-mentioned features of the first aspect of the present invention, the receiving member receives a superfluous amount of resin, which flows outside between the forming mold and the substrate. The superfluous amount of resin, which is received by the receiving member, is cured together with the resin as applied on the mold body so that the superfluous amount of resin cured is peeled from the forming mold together with the lens sheet as the finished product. It is therefore possible to prevent formation of the next lens sheet from being disturbed by the superfluous amount of resin and a traveling passage for the forming mold and the other equipment from becoming dirty.
In the second aspect of the present invention, said mold body may comprise a molding plate and a supporting plate on which said molding plate is secured. According to such a feature, the supporting plate and the receiving member impart a sufficient rigidity to the molding plate, thus reinforcing the molding plate.
In the third aspect of the present invention, a gap between said mold body and said receiving member may be filled with filler. According to such a feature, the filler prevents a superfluous amount of resin from coming into the gap between the mold body and the receiving member. This prevents the superfluous amount of resin from being left inappropriately on the forming mold after the lens sheet is peeled therefrom.
In the fourth aspect of the present invention, said receiving member may have a portion, which comes into contact with said mold body, said portion has a downward inclined upper surface in a direction from said mold body to said receiving member. According to such a feature, it is possible to cause the superfluous amount of resin to flow smoothly on the receiving member.
In the fifth aspect of the present invention, said mold body may have a portion, which comes into contact with said receiving member, said portion having a downward inclined upper surface in a direction from said mold body to said receiving member. According to such a feature, it is possible to cause the superfluous amount of resin to flow smoothly on the receiving member.
In order to attain the aforementioned object, the method of the sixth aspect of the present invention for manufacturing a forming mold for a lens sheet, comprising the steps of:
cutting four sides of a blank body having a basic plane in a direction perpendicular to said basic plane to prepare a mold body having on a periphery thereof four perpendicular side surfaces; and
securing a receiving member on at least one of said four perpendicular side surfaces of said mold body to prepare a mold unit, said one of said four perpendicular side surfaces being located on a pressing-finishing side.
According to the above-mentioned features of the sixth aspect of the present invention, the four sides of the blank body are cut in the direction perpendicular to the basic plane of the blank body so as to provide the mold body having the four perpendicular side surfaces. It is therefore possible to make a gap between the perpendicular side surface of the mold body and the receiving member small, thus preventing the superfluous amount of resin from being left on the forming mold.
In the seventh aspect of the present invention, said mold body may comprise a molding plate and a supporting plate on which said molding plate is adhered. According to such a feature, the supporting plate and the receiving member impart a sufficient rigidity to the molding plate, thus reinforcing the molding plate.
In the eighth aspect of the present invention, the method may further comprise subjecting said mold unit to a cutting work to form a downward inclined upper surface in a direction from said mold body to said receiving member at a connection portion of said mold body and said receiving member. According to such a feature, it is possible to cause the superfluous amount of resin to flow smoothly and rapidly on the receiving member.
In the ninth aspect of the present invention, the method may further comprise applying filler in a gap between said mold body and said receiving member prior to said securing of said receiving member. According to such a feature, it is possible to seal the gap between the mold body and the receiving member in an appropriate manner.
In the present invention, the xe2x80x9cforming moldxe2x80x9d means a device for forming or molding a lens sheet and includes a forming die.